This invention relates to blinds and more particularly to the manufacture of a kind of a flexible resilient synthetic resin with fibers or fabric.
While it has heretofore been proposed to make such blinds of plastic or aluminum, these have been subject to a number of disadvantages, those of which are excessive thickness and weight insufficiency or absence of resiliency and distortion including sagging and twisting.
There are also a number of disadvantages to conventional plastic (PVC) fabric in connection with prior art, those including lack of visual attractiveness, being brittle due to environmental effect, changing color due to age; there are a number of disadvantages in relation to aluminum fabric, those of which are relatively high cost, and, not being aesthetically pleasing. If fabric is used to make vertical blinds, a small part of its bottom should be turned up and a main weight should be inserted in its turned up pocket space in order to increase the verticality of the said fabric and prevent it from oscillation due to wind blowing. In addition, at the bottom of the said fabric vertical blind, ball-chains are connected each other for the convenience of operating the blinds.
An exemplary method such as this is illustrated in U.S. Pat. No. 4,324,832 covering a method of impregnating web structures with a synthetic resin. The said patent uses a solution of a mixture of different acrylic acid esters and aminoplast resins to impregnate a fibrous web structure. Although the fabric treated by this kind of solution possesses flexibility and strength, the fabric processed by conventional method may not be used in vertical blinds and venetian blinds due to the following two disadvantages: (1) If it is flexible, then it will be insufficiently strong, thus the blind will be easily bent and distorted; (2) If it possesses hardness only, it will become brittle easily, which will be more apparent at low temperature in particular.
U.S. Pat. No. 4,500,606 uses phenol formaldehyde resin, epoxy resin and polyvinyl formaldehyde resin to improve the adhesion between plastic leathers, and these resins are just only adhesive agents for plastic internals. However, the present invention is for the sake of textile surface treatment. Therefore, there is a big functional difference in comparison with the said U.S. patent. Moreover, the phenol formaldehyde resin and epoxy resin used in the said U.S. patent easily become brittle and yellowish in the air and are obviously different from the melamine resin and acrylic resin used in the present invention which are brittle-resistant and yellowish resistant. The phenol formaldehyde resin and epoxy resin used in the said U.S. patent are thermosetting resins only, but the present invention uses both the thermosetting resin (e.g. melamine resin) and thermoplastic resin (e.g. acrylic resin). Obviously there is a big difference in the utilization object. Although the said U.S. patent uses also polyvinyl formaldehyde resin, from its description one can clearly see that it uses high polymeric polyvinyl formaldehyde resin which should be dissolved in advance by solvent, but the present invention uses reasonably priced and highly safe aqueous polyvinyl formaldehyde resin (please refer to the Patent Bulletin No. 131894 of the Republic of China). Therefore, there is a remarkable difference between polyvinyl formaldehyde resin used.
Regarding "Comprehensive Polymer Science", the material described in page 51 to page 77 is polyvinyl acetate and does not use polyvinyl acetal. Obviously there is difference between the present invention and what is well-known.
Therefore, the main object of the present invention is to provide a blind fabric wherein the foregoing disadvantages are reduced to a minimum.